Rivet detecting apparatus

ABSTRACT

A rivet detecting apparatus having upper and lower annular clamps engaging the workpieces to be riveted and upper and lower anvils positioned in the upper and lower clamps. The upper anvil abuts the headed end of a rivet and is held stationary while the lower anvil is moved against the shank end of the rivet to form a head thereon. The lower anvil is spaced upwardly from a drive ram and is urged upwardly against the work by a spring. When a rivet is inserted in a hole formed in the workpieces, the lower shank end of the rivet engages the lower anvil and moves it downwardly against the spring bias. Downward movement of the lower anvil engages a movable plunger which actuates a limit switch to move the drive ram against the lower anvil and force it upwardly against the shank end of the rivet to form a head thereon. In the absence of a rivet in the rivet hole, the lower anvil remains in its uppermost position, the limit switch is not actuated, and operation of the riveting machine is terminated.

United States Patent [72] lnventor Harry P. Focht Kenmore. N.Y. [2 l] Appl. No. 847,930 {22] Filed Aug. 6, 1969 [45] Patented Apr. 13, 1971 [73] Assignee General-Electro Mechanical Corp.

Buffalo, N.Y.

[54] RIVET DETECTING APPARATUS 243.53, 243.54; 227/6, 7; 72/(lnquired); 10/1555 (curso y); 192/125 (E) [56] References Cited UNITED STATES PATENTS 2,406,463 8/1946 Jorgensen 192/ 1 25B 2,439,323 4/1948 Tuttle 29/243.54

Franz 192/1255 ABSTRACT: A rivet detecting apparatus having upper and lower annular clamps engaging the workpieces to be riveted and upper and lower anvils positioned in the upper and lower clamps. The upper anvil abuts the headed end of a rivet and is held stationary while the lower anvil is moved against the shank end of the rivet to form a head thereon. The lower anvil is spaced upwardly from a drive ram and is urged upwardly against the work by a spring. When a rivet is inserted in a hole formed in the workpieces, the lower shank end of the rivet engages the lower anvil and moves it downwardly against the spring bias. Downward movement of the lower anvil engages a movable plunger which actuates a limit switch to move the drive ram against the lower anvil and force it upwardly against the shank end of the rivet to form a head thereon. In the absence of a rivet in the rivet hole, the lower anvil remains in its uppermost position, the limit switch is not actuated, and operation of the riveting machine is terminated.

Patented April 13, 1971 3,574,918

AT TOQNEYS 1 RIVET DETECTING APPARATUS This invention relates to a riveting apparatus and, more particularly, to a rivet detecting mechanism for detecting the presence of a rivet in a riveting apparatus to avoid operation of the apparatus when a rivet has not been inserted in the rivet hole.

In conventional riveting, a rivet is inserted in a receiving hole formed in overlapping workpieces clamped together at their opposite sides by opposed clamping. The opposed clamping members are generally annular to accommodate an upper bucking tool or anvil and a lower rivet head forming anvil. The upper anvil is placed against the headed end of the rivet as a backup member while the lower anvil is forced upwardly by a power ram to upset the shank end of the rivet and form a head thereon.

Generally the upper anvil is associated with a rivet gripping means in the form of fingers commonly known as an injector, which receive successive rivets from a rivet feed conveying system and transfers them to a position along the riveting axis with the upper anvil in position above the upper clamping member. The anvil and fingers are then lowered within the hollow clamping member to place the rivet in its corresponding hole. The fingers are withdrawn laterally out of the way while the upper anvil is locked or securely held in position against the headed upper end of the rivet to provide a backup member for the impact tool driven from the opposite direction against the lower shank end of the rivet.

It is known to employ rivet detecting devices in such riveting machines to indicate the presence of a rivet in the injector. However, it is possible for the rivet to become displaced or dropped from the injector or rivet grasping finger assembly after such detection has occurred and before the rivet has been positioned at the rivet station so that the upper and lower anvils continue through their cycle in the absence of a rivet in the overlapping workpieces. Thus, the impact tool, which is generally the lower anvil, will be rammed upwardly against the workpiece rather than a rivet. The force of the impact against the surface of the workpiece can easily deform and damage the workpiece which may be an expensive aircraft component such as a fuselage, a wing panel, or the like.

SUMMARY OF THE INVENTION The apparatus of the present invention, as hereinafter described, provides a solution to the above problem by providing means for positively detecting the presence of a rivet in its final workpiece-engaging position and to initiate operation of the power ram which actuates the rivet head forming anvil only in response to a signal which indicates that the rivet is present in the rivet hole.

Generally speaking, the rivet detecting apparatus of the present invention is incorporated in a riveting machine and employs various elements of the riveting machine along with anvil-movement-responsive means for initiating movement of the power ram. The rivet detecting apparatus comprises a lower rivet head forming anvil engageable by the power ram for movement therewith toward an upper anvil which serves as the rivet bucking or backup tool. The lower anvil and the ram are urged apart by a spring means and with fluid pressure removed from the lower anvil, the spring means biases the lower anvil against the workpiece around the rivet receiving hole.

When a rivet enters the rivet hole in the workpieces, it forces the lower anvil downwardly against the spring bias. As the lower anvil moves downwardly, the lower end thereof actuates a limit switch for energizing a control circuit which initiates upward movement of the power ram to force the lower anvil upwardly against the shank end of the rivet and upset the lower end thereof, forming a head thereon. In the absence of a rivet, the lower anvil will not be lowered and the limit switch will therefore not be actuated to initiate movement of the power ram, and operation of the riveting machine is prevented.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevation view, partly in cross section, illustrating the work clamping members and the lower rivet forming tool of the present invention;

FIG. 2 is a view similar to FIG. 1 showing the rivet hole forming operation;

FIG. 3 is a view similar to FIG. 1 showing the lower anvil in its uppermost work engaging position;

FIG. 4 is a view similar to FIG. 1 illustrating the insertion of a rivet in its associated hole with the lower anvil positioned below the workpiece; and

FIG. 5 is a view similar to FIG. 1 showing the lower anvil in its rivet head forming position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT,

Referring now in detail to the drawings, there is shown in FIG. 1 a pair of overlapping sheet metal workpieces l0 and 12 securely clamped between an upper clamping sleeve 14 and a lower clamping sleeve 16. One of the clamping sleeves l4 and 16 is movable away from the other for insertion of workpieces between riveting operations. The terms upper, lower, top, bottom, and the like, as used herein, are applied only for convenience of description and refer to the orientation of the riveting structure as shown in FIGS. 1 through 5, and should not be taken as limiting the scope of this invention, it being understood that such structure may be oriented horizontally, if desired, or in a reverse vertical arrangement.

Also, it is to be understood that the work clamping, rivet detecting, and rivet forming mechanism hereinafter described is incorporated in a conventional riveting machine, not shown, but well known in the art. Since the rivet blank feeding and inserting mechanism are conventional and form no part of the present invention, the details of these mechanisms need not be illustrated herein.

A lower rivet head forming anvil 18 is received in lower clamping sleeve 16 for axial movement relative thereto. The upper end of anvil 18 is adapted to engage a rivet end for upsetting the same and forming a head thereon. The lower end of anvil 18 is provided with an annular enlargement 20 which acts as a piston vertically movable within an enlarged diameter portion 22 of lower clamping sleeve 16. Also received within enlarged portion 22 of sleeve 16 is a ram 24 mounted for axial movement relative to lower clamping sleeve 16. Vertical slots 26 are provided in ram 24 for receiving a transversely extending pin 28 secured to enlarged portion 22 of lower clamping sleeve 16 as by means of lock rings 30. The pin and slot arrangement permits limited axial movement of ram 24 relative to lower clamping sleeve 16.

A bore 32 in anvil 18 in registry with a bore 34 in ram 24 accommodates a helical spring 36 which tends to urge anvil l8 upwardly away from ram 24 as show in FIG. 3. A hardened steel wear washer 38 is carried by the upper end of ram 24 for engaging the lower end of piston 20 of anvil l8.

Piston 20 is recessed as at 40 and defines a chamber 42 within enlarged portion 22 of lower sleeve 16. Chamber 42 communicates with a port 44 (FIG. 1) provided in enlarged portion 22 for admitting air under pressure to chamber 42 or alternatively, evacuating air under pressure from such chamber. Also mounted in enlarged portion 22 of lower sleeve 16 is a movable plunger 46 secured to one side of a spring plate 48 mounted on the outer surface of enlarged portion 22 as by means of screws 50. A limit switch 52 is suitably mounted on the riveting machine adjacent to a spring plate 48 and is provided with a button actuator 54 engageable with spring plate 48 and movable thereby. Limit switch 52 is incorporated in an electrical circuit (not shown) for closing a control circuit which actuates or moves ram 24 upwardly to drive anvil 18 against a rivet.

The operation of the rivet detecting mechanism will now be described in conjunction with the operation of the hole drilling and rivet forming mechanisms. Referring now to FIG. I, the clamping sleeve 16 has been raised into work engaging 

1. Apparatus for detecting the presence of a rivet in a rivet hole extending through work to be riveted comprising a pair of clamping members relatively movable toward each other to clamp the work therebetween, a rivet head forming anvil, a ram operable to engage and move said forming anvil against a rivet end to form a head thereon, resilient means for biasing said anvil away from said ram and into a work engaging position; said anvil being movable away from said work by one end of a rivet inserted through said hole of said work, a bucking member abutting the other end of said rivet, and means responsive to movement of said anvil in a direction away from said work by said rivet for driving said ram against said anvil to move said anvil in an opposite direction against said one end of said rivet to form a head thereon.
 2. Apparatus according to claim 1 wherein said responsive means includes a limit switch and an operator therefor engageable by one end of said anvil upon movement thereof caused by said rivet engagement for actuating said limit switch and initiating operation of said ram.
 3. Apparatus according to claim 1 wherein said clamping members are annular and coaxial with said bucking member and said rivet head forming anvil.
 4. Apparatus according to claim 1 wherein said anvil is provided with an annular enlargement slidable within an enlarged portion of one of said clamping members and defining a chamber therewith.
 5. Apparatus according to claim 4 together with means for admitting air pressure into said chamber for moving said anvil against the bias of said resilient means into an initial position away from said work. 